The cause of the population reduction in this species (commercial whaling) is reversible, understood, and is not currently in operation. For this reason, the species is assessed under criterion A1, not under A2, A3 or A4. The analysis in this assessment estimates that the global population has declined by more than 70% over the last three generations (1929-2007), although in the absence of current substantial catches it is probably increasing. Most of the global decline over the last three generations is attributable to the major decline in the Southern Hemisphere. The North Atlantic subpopulation may have increased, while the trend in the North Pacific subpopulation is uncertain.